Ventilation system including a filter housing located outside the building

ABSTRACT

The invention relates to a ventilation system for a building ( 2 ) including an inlet ( 4 ) for outside air. According to the invention a filter housing ( 7 ) is located outside the building ( 2 ) and the outlet ( 13 ) from the filter housing ( 7 ) is connected to said inlet ( 4 ) for outside air.

TECHNICAL FIELD

The present invention relates to a ventilation system for a building including an inlet for outside air.

BACKGROUND OF THE INVENTION

The energy losses in a ventilation system consist typically from pressure losses in ducting, heat exchangers, cooling coils and similar equipment and also the specific performance of fans and air filters. A large part of the energy losses are due to the pressure drop over the air filters. Of the total energy used, the energy used by air filters generally amount to about 25-35% . The initial pressure drop and the development of pressure drop during the operation are the most important single factors that determine the energy consumption of an air filter. The initial pressure drop is easy to determine in tests or from manufacturers data sheets. However, equally important is how the pressure drop develops during the operation of the ventilation system. This is more difficult to predict since this is dependent on what kind of aerosol the filter is challenged to, what kind of filter mechanisms that are predominant in a filter and the quality of the filter. The quality and composition of the outdoor air vary a lot between different geographic locations and have a large influence on the service life of a filter. Air filters are normally replaced at regular intervals, usually once a year. Today the energy cost often is around 60-70% of the total operating costs of the air filters.

The objective of the present invention is to provide a ventilation system for a building including an inlet for outside air, in which the energy costs for the operation of air filters can be significantly reduced and in which the most suitable types of filters can be used.

SUMMARY OF THE INVENTION

This objective is accomplished by a ventilation system for a building including an inlet for outside air, characterized by a filter housing located outside the building, the outlet from the filter housing being connected to said inlet for outside air. By the arrangement of the filter housing outside of the building, the filter dimensions are no longer restricted by available space inside the building. Thereby, the velocity of the air passing through filter medium can be significantly reduced by increasing the area of the filter medium in relation to the area usually available for filter units arranged inside a building together with the other components of a ventilation system. The energy costs for such a ventilation system can be made very low. Such an arrangement of the filter housing also allows a choice of filter requiring a large area of the filter media, such as molecular filters. The cleaning of the outside air can thus be improved.

In a preferred embodiment, several filters units are accommodated in said filter housing and the inlets to said filter units are protected against wind and weather. Preferably, each of said filter units is accessible for replacement and maintenance by a separate door providing said protection against wind and weather.

Different types of filters can be accommodated within the filter housing.

The filter housing can be located on the roof of the building containing the ventilation system.

BRIEF DESCRIPTION OF THE DRAWING

The invention will now be described with reference to the enclosed figures, of which;

FIG. 1 schematically shows, in a partly sectioned side view, a building having a ventilations system according to a preferred embodiment of the invention, and

FIG. 2 schematically shows, in a perspective view, a filter housing for the air filters in the ventilation system according to FIG. 1.

DESCRIPTION OF EMBODIMENTS

In FIG. 1, a ventilation system for supplying conditioned air to rooms 1 to be ventilated in a building 2 having several rooms is schematically shown. Only a few of the rooms 1 in the building 2 are shown in FIG. 1. The ventilation system includes a central air-treatment unit 3 connected to an inlet 4 for outside air, ventilation ducts 5, which are connected to an outlet of the central air-treatment unit 3 and which have outlets leading into each room 1 to be ventilated in the building 2, and outlets from said rooms leading into air ducts 6 for passing air to the outside of the building. The central air-treatment unit can for example contain heat exchanger and an air cooler. The components in the ventilation system described above and the arrangement thereof are conventional.

According to the present invention a filter housing 7 is disposed outside the building 2 and the outlet from this housing 7 is connected to the inlet 4 which in turn is connected to the central air-treatment unit 3.

In FIG. 2, the housing 7 in FIG. 1 is shown in a larger scale and separated from the other components of the ventilation system of the building 2. The filter housing 7 includes five air inlet openings 8-12 and an outlet opening 13, which is connected to inlet 4 for outside air located on the roof of the building 2 by a suitable duct (not shown in FIG. 2). Each of the air inlet openings 8-12 of filter housing supports a particle filter unit 14 including a pleated filter medium 16 carried in a frame 15. One such filter unit 14 supported in inlet opening 8 is shown in FIG. 2.

The filter unit 14 can for example be a particle filter Hi-Flo® UF7 from Camfil AB., Trosa, Sweden or Hi-Flo® XLT7 or Hi-Flo® M9 from the same company.

In order to protect the filter units 14 from rain and wind, each air inlet opening 8-12 is protected by elements of the Venetian blind-type arranged on a door or frame 17 that is swingably attached to the associated inlet opening 8-12 so that the filter units 14 will be easily accessible for change thereof. In FIG. 2, the swingable frame 17 attached to opening 8 is shown in an opened condition whereas the other frames 17 covering openings 9-12 are shown in their closed operational condition.

By the arrangement of the filter housing 7 outside of the building 2, the filter dimensions are no longer restricted by available space inside building 2. Thereby, the velocity of the air passing through filter medium can be significantly reduced by increasing the area of the filter medium in relation to the area usually available for filter units arranged inside a building together with the other components of a ventilation system. Since the pressure drop through a filter is proportional to the square of the air velocity, a decrease of air velocity will significantly reduce pressure losses. The energy costs for the air filters in a ventilation system according to the present invention can thus be significantly decreased by increasing the area of the filters. Another advantage of lower air velocity is that fewer particles will be entrapped by the filter per unit of time. Consequently, the development (increase) of the pressure drop during operation of the ventilation system due to particles accumulated on the filter will be slower than at the higher air velocity. Thereby, the filters do not have to be changed as often as if the air velocity had been higher.

The pressure drop over air filter in known ventilation systems of today is often restricted by the performance of the fans in the system. The pressure drop over particle filters having high performance is higher than the pressure drop over particle filters having medium performance which means that for many ventilation systems of today high performance particle filters can not be used due to pressure drop restrictions. However, by using high performance particle filters with larger filter area such filters can without problem be used in a ventilation system according to the present invention. The present invention thus also allows an improved cleaning of the air taken from the outside of the building, thereby improving the air quality in the building.

The present invention also allows filters requiring a large surface, such as molecular filters, to be used in the ventilation system.

In a ventilation system according to the invention the energy costs for the air filters can thus be significantly reduced both in a short term and long term perspective. Furthermore, a free choice of type or types of filters is allowed and is not restricted by size limits. The ventilation system according to the present invention is thus very flexible and can be adapted to suit any demand.

The described embodiment can be modified in several respects without leaving the scope of invention. For example, other filters than stated above can be used and different types of and combinations of different types of filters can be used, such as a combination of particle filters and a molecular filter. The filter housing can have a different shape than in the shown embodiment and can contain more or less than five inlet openings. Instead of swingable frames, sliding frames can be used to protect the filters. The filter housing can be affixed to a wall of the building or be placed on the ground instead of being attached to the roof of the building. However, the filter housing should be placed near the inlet for outside air to of the building. A filter housing according to the present invention can also be used together with other ventilations systems than described above. A ventilation system according to the present invention can thus be accomplished by adding a filter housing according to the invention to an existing ventilation system in a building. The scope of invention shall therefore not be limited by the described embodiment but should only be restricted by the content of the enclosed patent claims. 

1. A ventilation system for a building including an inlet for outside air, the ventilation system comprising: a filter housing located outside the building and having an outlet, the outlet of the filter housing connected to said inlet for outside air.
 2. The ventilation system according to claim 1, wherein several filters units are accommodated in said filter housing, each filter unit having an inlet.
 3. The ventilation system according to claim 2, wherein the inlets to said filter units are protected against wind and weather.
 4. The ventilation system according to claim 3, wherein each of said filter units are accessible for replacement and maintenance by a separate door providing said protection against wind and weather.
 5. The ventilation system according to claim 1, wherein different types of filters are accommodated within the filter housing.
 6. The ventilation system according to claim 1, wherein the filter housing is located on the roof of the building containing the ventilation system.
 7. The ventilation system according to claim 2, wherein different types of filters are accommodated within the filter housing.
 8. The ventilation system according to claim 3, wherein different types of filters are accommodated within the filter housing.
 9. The ventilation system according to claim 4, wherein different types of filters are accommodated within the filter housing.
 10. The ventilation system according to claim 2, wherein the filter housing is located on the roof of the building containing the ventilation system.
 11. The ventilation system according to claim 3, wherein the filter housing is located on the roof of the building containing the ventilation system.
 12. The ventilation system according to claim 4, wherein the filter housing is located on the roof of the building containing the ventilation system.
 13. The ventilation system according to claim 5, wherein the filter housing is located on the roof of the building containing the ventilation system. 